1. Field of the Invention
The present invention relates to an in line plastic bag machine through which a web of double ply plastic film or sheet material, e.g. a tubular plastic sheet material, is fed. The web is trained over a shuttle mechanism which reciprocates within the machine beneath a head having at least one heat blade and one perforating blade. The movement of the shuttle is synchronized with the movement of the web so that the head is moved down over a platen while the shuttle is moving thereby to maintain the web momentarily stationary underneath the heat blade and perforating blade as it comes down on the platen with the web of double ply plastic sheet material extending therebetween. More specifically, the present invention relates to control mechanisms in a control system for controlling the speed of the drive rollers of the machine relative to the speed of an upstream web feeding machine. Also, the reciprocating speed of the shuttle is controlled by a control mechanism relative to the speed of the web passing through the machine. Further, the speed of rotation of a secondary drive roller or chrome roller is controlled by a control mechanism to move the web at a speed slightly greater or slightly slower than the speed of the main drive roller or chrome roller. Still further, a control mechanism controls the movement of the head downwardly into engagement with the web and momentarily holding at that position (dwell) for sealing and perforating the double ply web for sequentially forming bags in the web.
2. Description of the Prior Art
Heretofore various machines have been proposed for continuous high speed fabrication of plastic bags. Examples of these previously proposed analogous and non-analogous continuous high speed plastic bag fabricating machines are disclosed in the following analogous and non-analogous U.S. patents:
The Schott Jr. U.S. Pat. No. 4,003,298 is directed to a very early version of the machine described herein.
According to the present invention there is provided in an in line plastic bag machine comprising: first and second side walls; a plurality of rollers mounted between the side walls for receiving a web of plastic film that is trained through the machine over and around the rollers; a main drive motor; a main drive shaft driven by the main drive motor; the rollers including a main drive or chrome roller and a pair of spaced apart shuttle rollers mounted in a shuttle assembly; a drive train for driving from main chrome roller from the main drive shaft; the shuttle assembly being mounted for back and forth movement thereby to position an incremental width of the web of film traveling over the shuttle rollers in a momentary stationary position as the web of film is moving through the machine so that the incremental width of the film is momentarily stationery relative to the side walls; drive apparatus for moving the shuttle assembly; a perforating and sealing head which is movably mounted relative to the side walls for moving upwardly and downwardly over and relative to the incremental width of the web of film for sealing and perforating the incremental width of the web of film in cooperation with an underlying platen when the incremental width of web is momentarily stationary, thereby to sequentially form bags in the web of film; and head drive apparatus for moving the head; the improvement comprising electrical control circuitry for controlling the operation of the shuttle drive apparatus and the head drive apparatus relative to the speed of rotation of the main drive shaft.